1. Technical Field of the Invention
The present invention relates to the processing of the signals delivered by a pixel matrix of an image sensor, and more particularly the processing of the black level.
2. Description of Related Art
An image sensor in conventional manner comprises a pixel matrix. Each pixel delivers an electric signal, the level of which depends on the quantity of light received by the pixel. This signal is conventionally stored in a pair of sampling capacitors and then is amplified in a read amplifier.
An analog/digital converter makes an analog/digital conversion of each information element read and, for each image, digital words corresponding to the pixels of each line of the pixel matrix are delivered sequentially.
The black level (which is a pseudosignal due to the stray currents in the photodiodes of the pixels) is extremely variable depending on the technology, the temperature and the amplification gain used.
There is a need in the art to abstract from this black level, after evaluating it, the unprocessed signal of the sensor in order to isolate the true information from the sensor.
Another need in the art is to match the black level with a deterministic code at the output of the analog/digital converter in order also to allow optimized use of the analog/digital converter by avoiding digitizing this portion of offset containing no information.